Key Laboratory of Nuclear Solid State Physics of Hubei Province / School of Physics and Technology, Wuhan University,Wuhan 430072, Hubei, China
Abstract:
Formed in silica aerogels, positronium annihilation in oxygen and nitrogen mixture is studied by a simple and convenient method. The results show that ortho-positronium (o-Ps) lifetime is significantly shortened when some oxygen is introduced into nitrogen gas and that the o-Ps collisional quenching rate for an oxygen molecule is (28.0±0.4) μs?1·amagat?1 (1 amagat = 2.69×1025 m?3). It is found that the o-Ps annihilation rate in oxygen of 1atm at room temperature is (25.5±0.5) μs?1 and that the effective number of electrons per oxygen molecule available for 2γ annihilation of positron in the o-Ps is (34.6±0.4).
